A tire uniformity inspection machine is employed to make certain measurements used to characterize the uniformity of construction of a tire. This is accomplished in part by measuring the nature of reaction forces in various directions generated by the tire as it rolls under load along a surface as well as by measuring runout at selected loci on the surface of the tire.
In a typical tire uniformity inspection machine, testing is fully automatic. Tires are fed by conveyor to a test station where each tire is mounted upon a chuck, inflated to a predetermined pressure and rotatably driven at a standard speed with its tread surface in forced contact with the circumferential surface of the loadwheel. The loadwheel is instrumented with load cells which measure forces due to the tire acting on the loadwheel in directions of interest. Each rotation of the tire is divided into a series of 128 nominally equally angularly spaced points by a rotary shaft encoder. At each point, the analog output of the load cells and runout sensing devices are sampled so that each data sample corresponds to a particular location on the tire. The data samples are then used to compute various quantities such as the maximum, minimum or peak-to-peak force variation and runout. As used herein, the term "peak-to-peak" force variation or runout refers to the largest overall force or dimensional swing occurring over one revolution regardless of whether the maximum and minimum points which determine that swing are adjacent one another.